Avalanche, Sierra, Silverado, C&K Series, 1999-2005

8.1L V8 VIN G Auto 5

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Trouble Code: P1221



TP Sensor 2 Signal Correlation

Possible Causes:



TP2 sensor connector is contaminated, dirty or contains water
 
TP2 sensor signal, ground or VREF circuit has high resistance
 
TP2 sensor VREF circuit has a high resistance condition
 
TP2 sensor ground circuit has a high resistance condition
 
TP2 sensor is damaged or has failed
 
TAC controller or the throttle body is damaged or has failed
 
TSB 02-06-04-005 contains a repair procedure for this code
 

Trouble Code: P1280



Accelerator Pedal Position Sensor 2 Circuit Malfunction

Possible Causes:



APP2 sensor connector is contaminated, oily or contains water
 
APP2 sensor signal, ground or VREF circuit high resistance
 
APP2 sensor VREF circuit is open, shorted to ground or to B+
 
APP2 sensor signal or ground circuit has high resistance
 
APP2 sensor is damaged or has failed
 
TAC module is damaged or has failed
 

Trouble Code: P1281



Accelerator Pedal Position Sensor 2 Range/Performance

Possible Causes:



TP2 sensor connector is contaminated, oily or contains water
 
TP2 sensor signal, ground or VREF circuit has high resistance
 
TP2 sensor VREF circuit is open, shorted to ground or to B+
 
TP2 sensor signal or ground circuit has high resistance
 
TP2 sensor is damaged or has failed
 
TAC module is damaged or has failed
 

Trouble Code: P1285



Accelerator Pedal Position Sensor 3 Circuit Malfunction

Possible Causes:



APP3 sensor connector is contaminated, oily or contains water
 
APP3 sensor signal, ground or VREF circuit high resistance
 
APP3 sensor VREF circuit is open, shorted to ground or to B+
 
APP3 sensor signal or ground circuit has high resistance
 
APP3 sensor or the TAC module is damaged or has failed
 

Trouble Code: P1286



Accelerator Pedal Position Sensor 3 Range/Performance

Possible Causes:



APP3 sensor connector is contaminated, oily or moisture
 
APP3 sensor signal, ground or VREF circuit high resistance
 
APP3 sensor signal or ground circuit has high resistance
 
APP3 sensor or the TAC module is damaged or has failed
 

Trouble Code: P1336



CKP Sensor System Variation Not Learned

Possible Causes:



Set the parking brake and block the drive wheels for safety.
 
Verify the hood is closed.
 
Read the trouble codes. If a code is set, refer to that code.
 
Start the engine. Allow engine temperature to reach at least 158ºF (70ºC). Then key off.
 
Select Crankshaft Position Variation Learn procedure on Scan Tool & start the vehicle.
 
Apply the brake pedal firmly and verify the selector is in Park.
 
Increase accelerator pedal position until fuel cutoff is reached at the test rpm (e.g., 5150). Quickly release the accelerator pedal after fuel cutoff is reached. The CKP system variation compensating values are learned when the engine speed (rpm) decreases back to idle speed and the procedure terminates.
 
Read the trouble codes and recheck for DTC P1336.
 
If DTC P1336 runs and passes, the CKP system variation "learn" procedure is complete. If not, look for other codes. If no codes are set, repeat the test procedure.
 

Trouble Code: P1380



Misfire Detected, Rough Road Data Not Available

Possible Causes:



Use the Freeze Frame/Failure Records data to help find the cause on an intermittent fault. If the code cannot be duplicated, the data in the Freeze Frame/Failure Records can determine how many miles since the code set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the Freeze Frame conditions (i.e., load, engine and vehicle speed, temperature etc.). This will isolate when the code set.
 
Service the ABS before diagnosing a misfire because an actual engine misfire may or may not exist. Also, an actual engine misfire may have occurred during an ABS malfunction.
 
Determine if the vehicle was driven on a rough road, and the ABS could not detect this due to a malfunction. The PCM may interpret variations in crankshaft speed caused by the rough road as a misfire without an actual engine misfire present.
 
Refer to Diagnostic System Check for Antilock Brake System
 
Refer to Diagnostic System Check for the Engine Controls
 

Trouble Code: P1404



EGR Valve Closed Position Performance

Possible Causes:



EGR sensor signal circuit is shorted to VREF (5v)
 
EGR sensor ground circuit is open or has high resistance
 
EGR sensor is damaged or has failed (sensor/solenoid unit)
 
EGR valve pintle or valve seat contains carbon deposits
 
PCM has failed
 
TSB 01-06-04-043 contains a repair procedure for this code
 

Trouble Code: P1432



Fuel Pressure Sensor Circuit Low Input

Possible Causes:



Fuel tank pressure sensor is sticking or it is damaged
 
Fuel tank pressure sensor signal circuit is shorted to ground
 
Fuel tank pressure sensor is damaged or it has failed
 
PCM has failed
 

Trouble Code: P1433



Fuel Pressure Sensor Circuit Low Input

Possible Causes:



Fuel tank pressure sensor is sticking or it is damaged
 
Fuel tank pressure sensor signal circuit is shorted to ground
 
Fuel tank pressure sensor is damaged or it has failed
 
PCM has failed
 

Trouble Code: P1441



EVAP System Flow During Non-Purge

Possible Causes:



An improperly installed or damaged EVAP canister purge valve
 
A temporary blockage in the EVAP canister purge valve, purge pipe, or EVAP canister could cause an intermittent condition
 
FTP sensor is out-of-calibration, damaged or "skewed"
 
Purge solenoid valve is damaged or has failed
 
PCM has failed
 

Trouble Code: P1514



Throttle Body Performance

Possible Causes:



Inspect the throttle blade for damage and/or proper installation
 
Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple codes can set with no circuit or component faults apparent during diagnostic testing.
 
Physically and visually inspect the throttle body assembly, and throttle position sensor for damage and/or a loose mounting. Move the throttle blade from closed to wide open position without applying too much force. The throttle blade should move smoothly through the full range and should return to a slightly open position on its own.
 
If the TAC module detects a fault in the system, it may set more than one related code because of the many redundant tests that run continuously on this system. Locating and repairing one individual condition may fix more than one code.
 

Trouble Code: P1515



Control Module Throttle Actuator Position Performance

Possible Causes:



Throttle actuator motor CKT 1 is open, shorted to ground or B+
 
Throttle actuator motor CKT 2 is open, shorted to ground or B+
 
Throttle actuator motor is damaged or has failed
 
Throttle actuator motor control module has failed
 
TSB 00-06-04-035 contains a repair procedure for this code
 

Trouble Code: P1516



TAC Module Throttle Actuator Position Performance

Possible Causes:



TAC motor CKT 1 or CKT 2 is open, shorted to ground or B+
 
Throttle actuator motor CKT 1 is shorted to CKT 2
 
Throttle actuator motor control module has failed
 
TSB 03-04-06-034 contains a repair procedure for this code
 

Trouble Code: P1517



Throttle Actuator Control Module Performance

Possible Causes:



Test the charging system output (low voltage can set this code)
 
Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple codes may set without any circuit or component conditions found during diagnostic testing.
 
When the TAC module detects a fault condition, several TAC related codes set because there are redundant tests running.
 
TAC module has failed
 

Trouble Code: P1518



Throttle Actuator Control Module Serial Data Malfunction

Possible Causes:



DTC P1518 sets if the battery voltage is low. If the customer's concern is slow cranking or no crank due to low battery voltage, ignore the DTC P1518. Clear codes and retest.
 
DTC P1518 also sets when there is a short to B+ on the TAC module ground circuit. Inspect the fuses for the circuits that are in the TAC module harness (e.g., Brake & Cruise) for the fault.
 
DTC P1518 sets if the TAC module power circuit is shorted to a B+ supply circuit. The TAC module stays powered-up when the ignition switch is turned off. When the key on, the TAC module is powered-up before the PCM gets power. DTC 1518 is set because the TAC module did not detect signals from the PCM.
 
TAC module has failed
 

Trouble Code: P1631



Theft Deterrent - Start Enable Signal Not Correct

Possible Causes:



Refer to Diagnostic System Check for Theft Deterrent Module
 
Perform the Powertrain Onboard Diagnostic System Check
 
TSB 77-65-31 contains a repair procedure for this code
 

Trouble Code: P1635



5-Volt Reference 1 Circuit Malfunction

Possible Causes:



5v VREF circuit is shorted to sensor ground or chassis ground
 
5v VREF circuit, MAP or EGR sensor circuit is shorted to (B+)
 
5v VREF circuit shorted to EGR sensor High signal circuit
 
EGR solenoid valve (and sensor) is damaged or has failed
 
PCM has failed
 

Trouble Code: P1637



Generator 'L' Terminal Circuit Malfunction

Possible Causes:



A Scan Tool should display Inactive for the 'L' Terminal and 10-40% for the 'F' Terminal with the ignition "on". With the engine running, the display should indicate the 'L' Terminal is Active and the 'F' Terminal is higher than 5% on the tool display.
 
Generator 'L terminal circuit shorted to ground or to power (B+)
 
Generator 'F' terminal circuit is open or shorted to ground
 
Generator is damaged or has failed or the PCM has failed
 

Trouble Code: P1639



5-Volt Reference 2 Circuit Malfunction

Possible Causes:



5v VREF circuit is shorted to sensor ground or chassis ground
 
5v VREF circuit, FTP or TP sensor circuit is shorted to (B+)
 
5v VREF circuit shorted to FTP or TP sensor signal circuit
 
FTP sensor or TP sensor is damaged or PCM has failed
 

Trouble Code: P1810



TFP Valve Position Switch Assembly (4L60-E, 4L65-E, 4L80-E)

Possible Causes:



TFP valve position switch signal circuit is open, grounded or shorted to another signal
 
TFP valve position switch is damaged or has failed
 
This code can set during fluid refilling. After refilling the fluid, cycle the key "off", then idle the engine for 20 seconds. Turn the key "off" and allow the PCM to power down.
 
This code can set due to low pump pressure or due to a stuck pressure regulator.
 
This code can set due to a rolled forward clutch piston seal. It may allow the PCM to see a 2.08:1 ratio (reverse) when the manual valve position is actually indicated in D4.
 
PCM has failed
 

Trouble Code: P1860



TCM PWM Solenoid Circuit Malfunction (4L60-E, 4L65-E, 4L80-E)

Possible Causes:



TCC solenoid control circuit is open or shorted to ground
 
TCC solenoid control circuit is shorted to system power (B+)
 
TCC solenoid power circuit is open (test TRANS or IGN fuse)
 
TCC solenoid is damaged or has failed
 
PCM has failed
 

Trouble Code: P1870



Transmission Component Slipping (4L60-E, 4L65-E, 4L80-E)

Possible Causes:



1-2 shift solenoid valve has sediment, damage or leaking seals
 
2-3 shift solenoid valve has sediment, damage or leaking seals
 
3-2 shift solenoid valve has sediment, damage or leaking seals
 
Valve body regulator apply valve stuck or regulator is scored
 
Torque converter front stator shaft bushing is worn, the stator roller clutch is not holding or it has external damage/leaks
 
Converter clutch valve is stuck or it is installed backwards
 
Converter clutch valve retaining ring is not positioned properly
 
Converter clutch outer valve spring is cocked
 
Pump to case gasket is not positioned properly
 
Orifice cup plugs are restricted or damaged
 
Over-tightened, or unevenly tightened pump body to cover bolts
 
TSB 02-07-30-001 contains a repair procedure for this code
 

Trouble Code: P1875



4WD Low Switch Circuit Fault (4L60-E, 4L65-E, 4L80-E)

Possible Causes:



4WD low switch signal circuit is open, shorted to ground or B+
 
4WD low switch is damaged or has failed
 
PCM has failed
 

Trouble Code: P2108



Throttle Actuator Control Module Internal Data Test Failed

Possible Causes:



TAC module is damaged or it has failed
 

Trouble Code: P2120



Accelerator Pedal Position Sensor 1 Signal Performance

Possible Causes:



APP sensor connector is damaged, open or shorted
 
APP1 sensor signal circuit is open or shorted to ground
 
APP1 sensor signal circuit is shorted to APP sensor 2 circuit
 
APP1 sensor signal circuit is open or shorted to VREF (5v)
 
APP sensor is damaged or it has failed
 
TAC module is damaged or it has failed
 

Trouble Code: P2121



Accelerator Pedal Position Sensor 1-2 Correlation Malfunction

Possible Causes:



APP sensor connector is damaged, open or shorted
 
APP1 sensor low reference circuit is open or high resistance
 
APP1 sensor VREF circuit is open or shorted to ground
 
APP sensor is damaged or it has failed
 
TAC module is damaged or it has failed
 

Trouble Code: P2125



Accelerator Pedal Position Sensor 2 Circuit Malfunction

Possible Causes:



APP1 sensor signal circuit is open or shorted to ground
 
APP1 sensor signal circuit is shorted to APP sensor 2 circuit
 
APP1 sensor signal circuit is open or shorted to VREF (5v)
 
APP sensor is damaged, or the TAC module is damaged or it has failed
 

Trouble Code: P2135



Throttle Position Sensor 1-2 Correlation Error

Possible Causes:



TP1 sensor signal circuit shorted to TP sensor signal 2 circuit
 
TP1 sensor signal circuit is shorted to the low reference circuit
 
TP2 sensor signal circuit is shorted to the low reference circuit
 
Throttle body assembly is damaged or it has failed
 

Trouble Code: U1000



Class 2 Communication Malfunction

Possible Causes:



Class 2 circuit is open, shorted to ground or shorted to power
 
PCM ignition power circuit(s) has a high resistance condition
 
PCM main ground circuit(s) has a high resistance condition
 
SDM (module) could be shorted pulling the voltage low
 

Trouble Code: U1016



No Communication With Powertrain Control Module

Possible Causes:



PCM Class 2 circuit is open, shorted to ground or to B+
 
PCM ignition power circuit(s) has a high resistance condition
 
PCM main ground circuit(s) has a high resistance condition
 
PCM (module) may have failed and is pulling the circuit low
 

Trouble Code: U1026



Loss of ATC Class 2 Communication

Possible Causes:



Check for a loose connection at the ATC module
 
Test the main power and ground circuits to the ATC module
 
Check the Class 2 serial data circuit to the ATC module
 
ATC module may have failed
 

Trouble Code: U1041



Loss of Electronic Brake Controller Communication

Possible Causes:



Check for a loose connection at the EBCM (module)
 
Test the main power and ground circuits to the EBCM (module)
 
Check the Class 2 serial data circuit to the EBCM (module)
 
EBCM (module) may have failed
 

Trouble Code: U1048



No Communication With Rear Wheel Steering Control Module

Possible Causes:



RWSCM Class 2 circuit is open, shorted to ground or to B+
 
RWSCM ignition power circuit has a high resistance condition
 
RESCM main ground circuit(s) has a high resistance condition
 
RESCM (module) may have failed and is pulling the circuit low
 

Trouble Code: U1064



No Communication With Body Control Module

Possible Causes:



BCM Class 2 circuit is open, shorted to ground or to B+
 
BCM ignition power circuit has a high resistance condition
 
BCM main ground circuit(s) has a high resistance condition
 
BCM (module) may have failed and is pulling the circuit low
 

Trouble Code: U1088



No Communication With SDM (Restraint Module)

Possible Causes:



SDM Class 2 circuit is open, shorted to ground or to B+
 
SDM ignition power circuit has a high resistance condition
 
SDM main ground circuit(s) has a high resistance condition
 
SDM (module) may have failed and is pulling the circuit low
 

Trouble Code: U1092



Loss of VTD (Pass Lock) Communication

Possible Causes:



Check for a loose connection at the VTD module
 
Test the main power and ground circuits to the VTD module
 
Check the Class 2 serial data circuit to the VTD module
 
VTD module may have failed
 

Trouble Code: U1096



No Communication With Instrument Panel Cluster

Possible Causes:



IPC Class 2 circuit is open, shorted to ground or to B+
 
IPC ignition power circuit has a high resistance condition
 
IPC main ground circuit(s) has a high resistance condition
 
IPC (module) may have failed and is pulling the circuit low
 

Trouble Code: U1097



No Communication With Driver Information Center

Possible Causes:



DIC Class 2 circuit is open, shorted to ground or to B+
 
DIC ignition power circuit has a high resistance condition
 
DIC main ground circuit(s) has a high resistance condition
 
DIC (module) may have failed and is pulling the circuit low
 

Trouble Code: U1151



No Communication With Vehicle Interface Unit

Possible Causes:



VIU Class 2 circuit is open, shorted to ground or to B+
 
VIU ignition power circuit has a high resistance condition
 
VIU main ground circuit(s) has a high resistance condition
 
VIU (module) may have failed and is pulling the circuit low
 

 
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